Methods: Periodate-lysine-paraformaldehyde-fixed, EDTA-demineralized frozen sections were prepared from lower first molars of Wistar rats (n = 4). Double-labeling for microtubule-associated protein 1B (MAP1B) and CD146 using the avidin-biotin-peroxidase complex method was performed and the number of double-positive cells was enumerated. Moreover, real-time PCR analysis of CD146, CD105, and CD166 mRNAs was carried out in four regions (coronal pulp, distal root, pulp, mesial PDL, and distal PDL).
Results: MAP1B and CD146 double-labeled cells were identified in each region examined. However, the density of the double-labeled cells in the coronal pulp was significantly greater than that of the other regions (P < 0.05, Friedman test followed by Wilcoxon test with Bonferroni correction). Moreover, CD146, CD105, and CD166 mRNA expression levels were significantly higher in the coronal pulp compared with the other regions (P < 0.05, Friedman test followed by Wilcoxon test with Bonferroni correction).
Conclusions: The density of stem cell-related marker-expressing cells and stem cell-related gene expression levels were higher in the coronal pulp than in the root pulp and periodontal ligament, suggesting that the coronal pulp harbors more stem cells than the other regions.